The TCP/IP network protocols (e.g., the Transmission Control Protocol (TCP) and the Internet Protocol (IP)) were designed to build large, resilient, reliable, and robust networks. Such protocols, however, were not originally designed with security in mind. Subsequent developments have extended such protocols to provide for secure communication between peers (e.g., Internet Protocol Security (IPsec)), but the networks themselves remain vulnerable to attack (e.g., Distributed Denial of Service (DDoS) attacks).
Most existing approaches to protecting such networks are reactive rather than proactive. While reactive approaches may identify the source of an attack and assist in subsequent mitigation efforts, in most instances, the attack will have already been successfully launched.
Proactive solutions, however, have often been deemed untenable due to an inability to scale to larger networks. A significant challenge associated with building a scalable proactive solution is the need to filter substantially all network traffic at a high resolution. In a large network, where traffic volumes may be enormous, the time required to provide high resolution filtering has traditionally been thought to render a proactive solution infeasible.